It is well known to apply a primer coating or “topcoat” to a paper or film substrate in order to improve bonding or anchorage of subsequently applied inks, toner, or other materials to the substrate. The formulation of the coating typically depends upon numerous factors such as the nature of the substrate and the printing media, i.e. the inks, toner or other materials. The characteristics of the coating can also depend upon the particular type of printing process to be used in applying the ink or toner. Although numerous types of coatings are known, many of which provide satisfactory performance, a need remains for coating compositions which exhibit improved properties as compared to currently known compositions.
It would also be beneficial to provide primer or topcoat compositions which could be used in association with a variety of different printing processes. For example, in view of the increasing popularity of HP Indigo printing, UV printing, and inkjet printing; it would be desirable to provide a single class of compositions which could be used in all of these processes. That is, although certain compositions may provide satisfactory results for one type of printing process, frequently such results do not extend to use of the same composition to other printing processes.
More specifically, ink anchorage for HP Indigo printing applications is typically poor and difficult to achieve for certain substrates. This is believed to be due to at least two factors. One factor may relate to the type of substrate. For example, it is difficult to achieve good topcoat adhesion to certain substrates such as polypropylene and cast gloss paper. A second factor relates to compatibility difficulties between many inks and the topcoat. For HP Indigo printing techniques, the topcoat must be relatively polar and compatible with the ink to be applied thereto. Therefore, it would be beneficial to provide a topcoat which exhibits good adhesion to substrates such as polypropylene and cast gloss paper; and which is relatively polar and compatible with inks typically used in HP Indigo printing.